Develop Reference

How to get a ConstraintSet working inside a programatically generated ConstraintLayout descendant?

I have a view that inherits from ConstraintLayout. Inside this layout I place the children by use of a ConstraintSet.
This works as long as use a given AttributeSet form outside in the constructor:
public AnswerView(Context context, AttributeSet attrs) {
super(context, attrs);
It does not work, if I try to assign the layout otherwise, when I don't have attrs available.
public AnswerView(Context context) {
super(context);
setLayoutParams(new LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT));
In the first case the children get a pretty distribution like defined by the ConstraintSet, in the second case the all line up at the left border.
In both cases the layout stretches full width, as I can prove by setting a background color.
What is missing in my code?

This is not a direct answer to the question. A direct answer is still missing. This answer is of the type, "take a better approach!".
When there are few or no answers to a question, I am usually on a track, that few people go. Then there are reasons why they don't.
My approach to programatically nest views within other views is cool, but it turns out to be difficult to do this without the use of layouts. It's too expensive to set up all the benefits of the configurations programatically, that can easily done within a layout. The API of Android is not well prepared for this.
So I turned back to the approach, to create the view classes based on layouts. This means, I create the view with the two parameter constructor for layouts.
In the enclosing view class I can't create the nested view directly any more, as there is no constructor for this. Instead I read the configured view from a layout.
I created a small class to assist extracting configured subparts of a layout:
public class Cloner {
LayoutInflater inflater;
int layoutId;
public Cloner of(Context context) {
inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
return this;
}
public Cloner from(#LayoutRes Integer layoutId) {
this.layoutId = layoutId;
return this;
}
public View clone(#IdRes int id) {
assert inflater != null;
View layout = inflater.inflate(layoutId, null);
View view = layout.findViewById(id);
((ViewManager) view.getParent()).removeView(view);
return view;
}
}
It is used like this:
MultipleChoiceAnswerView mcav =
(MultipleChoiceAnswerView) new Cloner().of(getContext())
.from(layoutId).clone(R.id.multipleChoiceAnswerView);
mcav.plugModel(challenge.getAnswer());
This already shows, how I connect the model in a second step, because I can't feed it into by the constructor any more.
In the constructor I first evaluate the given attributes. Then I set up the view by inflating an accompanying second layout file, that I don't show here. So there are two layouts involved, one to configure the input to the constructor, one for the internal layout.
When the call to plugModel happens, the inflated internal layout is used and extended by objects matching the given model. Again I don't create this objects programatically, but read them from a third (or the second) layout file as templates. Again done with the assistance of the Cloner given above.
private Button getButton(final Integer index, String choice) {
Button button = (Button) new Cloner().of(getContext()).from(layoutId).clone(R.id.button);
button.setId(generateViewId());
button.setText(choice);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
answer.choiceByIndex(index);
}
});
return button;
}
In practice I put this object templates (like a button) as children into the second layout file. So I can style it as a whole in Android Studio Designer.
Programatically I remove the templates before I actually fill the layout with the cloned objects. By this approach I only need to maintain one layout file per view class. (The configuration of the constructor happens in the layout file of the enclosing view.)

Dynamically add a button to a view from a listview Adapter GetView method

As a little eperiment, I'm trying to do the following.
I have an AXML describing a vertical linear layout which contains a listview (only filling 200dp of the vertical linear layout ). The AXML is inflated when the activity starts with SetContentView. Then the listview is correctly populated with values using its Adapter.
In the GetView method of the listview Adapter, I am trying to also dynamically create a button and add it to the linear layout, but for some reason the button is not added.
If I try to add the button in the constructor method of the Adapter instead, it is correctly added.
Can you tell me what could be possibly going wrong?
Let me add some code:
class TracksAdapter : BaseAdapter<string> {
Activity context;
List<Dictionary<string,string>> trackList;
// constructor
public TracksAdapter (Activity context, List<Dictionary<string,string>> trackList) {
this.context = context;
this.trackList = trackList;
// Just as a little test, if I create the button from here it will be correctly added to linear layout:
var ll = context.FindViewById<LinearLayout>(Resource.Id.linLayForResultsActivity);
Button b1 = new Button(context);
b1.Text = "Btn";
ll.AddView(b1);
}
public override View GetView(int position, View oldView, ViewGroup parent) {
// if I create the button from here it will not be added to the layout
var ll = context.FindViewById<LinearLayout>(Resource.Id.linLayForResultsActivity);
Button b1 = new Button(context);
b1.Text = "Btn";
ll.AddView(b1);
// this other code is working
View view = context.LayoutInflater.Inflate(Resource.Layout.ResultItem, null);
var artistLabel = view.FindViewById<TextView>(Resource.Id.resultArtistNameTextView);
artistLabel.Text = trackList[position]["trackArtistName"];
return view;
}
}
Update: adding some more context information because I know this can be a bit weird to understand without it:
In GetView, I don't need to return the new button I am trying to create there. GetView only need to return a listview view item, but, along its execution, GetView also has to create and add a button to the linear layout containing the listview.
The real code is much more complex than that. I have simplified it in the question. In the real code, the listview items are made of text and a button. The GetView also attaches event handlers to the buttons. Then what I need is, when a user clicks a button in any of the listview items, another button is added below the listview. So I need the code for adding another button to be in GetView, and the button needs to be added outside of the listview, ie. to the linear layout containing the listview.

Use the LayoutInflator to create a view based on your layout template, and then inject it into the view where you need it.
LayoutInflater vi = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = vi.inflate(R.layout.your_layout, null);
// fill in any details dynamically here
TextView textView = (TextView) v.findViewById(R.id.a_text_view);
textView.setText("your text");
// insert into main view
ViewGroup insertPoint = (ViewGroup) findViewById(R.id.insert_point);
insertPoint.addView(v, 0, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));

I looked in you code, you are returning view, while you add the button to ll, you should return ll
what you return in getView() is what you see in the list item layout, since you're adding the button to ll and returning view, the button won't appear.
you can add the button to view as you implementation
Also check this:
Try using boolean addViewInLayout (View child, int index, ViewGroup.LayoutParams params)
http://developer.android.com/reference/android/view/ViewGroup.html#addViewInLayout(android.view.View, int, android.view.ViewGroup.LayoutParams)

It's working... Without making any changes now it's working as it should... ! Ugh!
I really don't know what I was doing wrong here... probably it was because of some sort of caching of older version of the installed APK.. ? I know this sort of stuff can happen, and that's why I've always been uninstalling the app before deplyoing the new version to the device... but still...!

Adding a View makes a ListView within a fragment to refresh

This might be a little bit hard to explain, so the best way I can think of, is providing you a Video showing up the issue.
In the Video I show myself scrolling listview, and after 5 seconds, a View is created and added inside that holder in the bottom. In that moment, listview is refreshed.
http://tinypic.com/player.php?v=vpz0k8%3E&s=8#.U0VrIvl_t8E
The issue is the following:
I've an Activity with a layout that consists of a:
Fragment (above RelativeLayout), match parent, match parent.
RelativeLayout, as wrap content.
The fragment displays a ListView with animations for every row.
If I add a View on the "RelativeLayout", it makes the fragment to readjust to the new size, as it's set above this RelativeLayout, so every Row is rebuilt again.
Do you guys think in any way to avoid this?
EDIT: Sourcecode:
https://bitbucket.org/sergicast/listview-animated-buggy

Don't start the animation if the layout process for the added footer view is running. The end of the layout process can be determined using the ViewTreeObserver (the start obviously starts with adding the footer view):
hand.postDelayed(new Runnable() {
#Override
public void run() {
ViewTreeObserver viewTreeObserver = holder.getViewTreeObserver();
viewTreeObserver.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
#SuppressWarnings("deprecation")
#Override
public void onGlobalLayout() {
holder.getViewTreeObserver().removeGlobalOnLayoutListener(this);
mIgnoreAnimation = false;
}
});
mIgnoreAnimation = true;
holder.addView(viewToAdd);
}
}, 5000);
Add this method to your Activity:
public boolean ignoreAnimation() {
return mIgnoreAnimation;
}
And check it in your Fragment:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
Context context = FragmentTest.this.getActivity();
TextView tv = new TextView(context);
tv.setText("Pos: " + position);
tv.setTextSize(35f);
if (runAnimation()) {
Animation anim = AnimationUtils.loadAnimation(context, R.anim.animation);
tv.startAnimation(anim);
}
return tv;
}
private boolean runAnimation() {
Activity activity = getActivity();
if (activity != null && activity instanceof MainActivity) {
return ! ((MainActivity)activity).ignoreAnimation();
}
return true;
}
Of course the whole Activity - Fragment communication can be improved considerably but the example gives you the idea how to solve the problem in general.
While it prevents the animation from being started, it doesn't prevent the ListView from being refreshed although the user won't notice. If you are concerned about performance you can improve the Adapter code by re-using the views:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
Context context = FragmentTest.this.getActivity();
TextView tv = null;
if (convertView != null && convertView instanceof TextView) {
tv = (TextView) convertView;
}
else {
tv = new TextView(context);
}

Yes, I can think of a possible way to solve this.
Your problem is:
You have set layout params of your holder to wrap_content. By default, when it has no content, it is "zero-sized" somewhere in the bottom and invisible to you (not invisible in terms of Android, though, sic!)
When you add a View to this holder, the framework understands, that the size of your holder container is different now. But this container is a child of another container - your root RelativeLayout, which, in turn, contains another child - your <fragment>.
Thus, framework decides, the root container alongside with its children should get laid out again. That's why your list gets invalidated and redrawn.
To fix the issue with list getting invalidated and redrawn, simply specify some fixed layout parameters to your holder. For example:
<RelativeLayout
android:id="#+id/holder"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true" >
</RelativeLayout>
That will prevent the list from being redrawn. But in that case you'll get your holder displayed from the very beginning.

Yes. This is the expected behavior of RelativeLayout
You are adding the ListView Fragment and TextView into a RelativeLayout, So whenever there is a change in the child view dimension, will affect the other child in the RelativeLayout.
So here when you add a new TexView , the other child Fragment is affected even though its height is match_parent.
You can fix this only by changing the parent layout to LinearLayout.

Gallery: Effect in item selected

I need to have an scroll with items together, and the selected item should expand a part down.
I am currently using a Gallery (I tried with viewflow and viewpager, but the items have much space between them), but I need to know how can I do this effect.
I have 2 ideas, but i don't know how can I implement it.
1) The expandable part is a LinearLayout with visibility=gone, and when the item is selected, this layout should be visible. (Gallery do not have "onItemSelectedListener")
2) Treat each element as a fragment (once I use a Viewpager that use this, https://github.com/mrleolink/SimpleInfiniteCarousel)
It does not necessarily have to be a gallery, any idea is welcome
I am working on an Activity.

Depends on the behavior that you want. Some questions can more than one item be expanded at a time? Do you want the views to be paged (snap into place) or smooth scroll them?
One Suggestion I have is to make a custom view for the individual cells. Then add them programmatically to a HorizontalScrollView Object.
HorizontalScrollView hsv = new HorizontalScrollView(activity);
LinearLayout hll = new LinearLayout(activity);
hll.setOrientation(LinearLayout.HORIZONTAL);
for(int i=0;i<items.length();i++){
hsv.addView(new CustomExpandView(item));
}
The CustomExpandView would be used for your cells and could be something like this...
public class CustomExpandView extends RelativeLayout implements OnClickListener {
MyActivity mActivity = null;
ImageView ivImage, ivOverImage;
RelativeLayout rlView;
public CustomExpandView(Context context) {
super(context);
initialize();
}
public CustomExpandView(Context context, AttributeSet attrs) {
super(context, attrs);
initialize();
}
public void initialize() {
mActivity = (MyActivity) this.getContext();
LayoutInflater inflater = (LayoutInflater) mActivity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater.inflate(R.layout.custom_cell_expand, this, true);
//you can initialize subviews here
rlView = (RelativeLayout) getChildAt(0);
ivImage = (ImageView) rlView.getChildAt(0);
ivOverImage = (ImageView) rlView.getChildAt(1);
rlView.setOnFocusChangeListener(new OnFocusChangeListener(){
#Override
public void onFocusChange(View v, boolean hasFocus) {
LinearLayout expand = v.findViewById(R.id.view_i_want_to_expand);
if(hasFocus)
expand.setVisibility(View.VISIBLE);
else
expand.setVisibility(View.GONE);
}
});
}

You gave the answer yourself. You can use a ViewPager, with fragments, and have an animation to extend the lower part of the window. Depends on whether you want the windows to be full screen or not. A viewpager doesn't necessarily need fragments, you can use ordinary views, and an appropriate adapter. Just play with it and see which solution you like most.
Next time, just create the code and the app, and ask a much more specific question, with code to illustrate the issue you're experiencing.

You could simply define a TableView with just one TableRow (or as many as you need) and set a onClickListener for each of those Views inside the TableRow, which would make that on any click, the selected View would expand itself.
I don't know whether you'll have a static number of Views inside that row or you'll construct them dynamically, but this should work for any of them, the real "work" here about populating that row.
Once you have your row of Views, simply declare an onClickListener() on each of them. For example, this should be enough:
OnClickListener myListener = new OnClickListener() {
#Override
public void onClick(final View v) {
v.setVisibility(View.VISIBLE);
}
};
And as the onClick event for all of your items inside the TableRow:
for (View v : myTableRowViews)
v.setOnClickListener(myListener);
This has a disadvantage: You can know which View has been clicked for selection, but natively you cannot know which has been deselected, so you'll need to keep track of the last selected tab declaring a class-wide variable and setting it each time onClick() is fired, so your listener will become something like this:
// In your class declare a variable like this
View lastSelected = null;
OnClickListener myListener = new OnClickListener() {
#Override
public void onClick(final View v) {
if (lastSelected != null)
lastSelected.setVisibility(View.GONE);
v.setVisibility(View.VISIBLE);
lastSelected = v;
}
};
Additionally, you can set an animation to the effect to make it more attractive, but mainly this is the idea.
One last thing: To make it work this way you'll need to set the layout_height of both your TableRow and the View items inside, so it may expand afterwards when you set the additional part as visible. Also, to make it look good all of your Views will have to be the same height (both in the reduced and extended state).

How can I inflate a View subclass from XML?

I am currently populating an Adapter on startup with views inflated from XML using
private void addView(Context context) {
LayoutInflater inflater = LayoutInflater.from(context);
View view = inflater.inflate(R.layout.deal_tile, this, null);
mViews.add(view);
}
However, I've found that storing the views in a list inside the AdapterView creates problems with controls within those views, so I want to change over to use the recycling functions in Adapter#getView(int position, View recycle, ViewGroup container).
For this reason I want to use a custom view class so I can do a sanity check (if(recycle!=null && recycle instanceof CustomView)) before I repopulate it in the adapter. However, I can't find out how you inflate a custom view class from XML. I can find out how you add an inflated view to a custom view, I can find out how you insert a custom view into an XML layout, etc, and obviously I am quite happily inflating these things directly using LayoutInflater, but I can't find an equivalent for generating the custom view itself. I want to reuse the XML I already have; consequently I don't want to program in the elements (and how they look) directly.

I used this to create my own slide gallery, i think it would help.
LinearLayout internalWrapper = new LinearLayout(getContext());
internalWrapper.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
internalWrapper.setOrientation(LinearLayout.HORIZONTAL);
addView(internalWrapper);
this.mItems = items;
LinearLayout generalLayout = new LinearLayout(this.getContext());
generalLayout = (LinearLayout) View.inflate(this.getContext(), R.layout.galleryrow, null);
// inside linear layout
LinearLayout generalLinear = (LinearLayout) generalLayout.findViewById(R.id.rowgenerallin);
// set height & width to the LINEAR
generalLinear.setLayoutParams(new LayoutParams(reference_width, reference_height));
ImageView ivl = (ImageView) generalLayout.findViewById(R.id.arrow_left);
ImageView ivr = (ImageView) generalLayout.findViewById(R.id.arrow_right);
internalWrapper.addView(generalLayout);
In my case, R.layout.gallery_row contains the two images I want to manage, nested by a LinearLayous (rowgenerllin), the internal wrapper is an empty LinearLayout declared in the main layout of your activity.
Double check the LayoutParams code or you will get a big NULL :)
Cheers!